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# Which Way: How Can You Identify the Poles of an Unmarked Magnet?

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Source:
Author: Janice VanCleave

### Problem?

How can you identify the poles of an unmarked magnet?

### Materials

• 3 sheets of paper
• compass
• marking pen
• scissors
• ruler
• paper hole-punch
• string
• bar magnet

### Procedure

NOTE: Never touch a compass with a magnet. Touching a compass with a strong magnet can change the polarity of the compass needle, causing the end marked north to become a south pole and all directions to be reversed.

1. Make a paper compass by taping one sheet of paper to the top of a wooden table. Be sure that there are no magnetic materials on or near the table.
2. Place the real compass in the center of the paper.
3. Use the marking pen to draw marks on the paper at the four main compass points (N, E, S, and W).
4. Remove the real compass. With your pen, connect the paper compass points with straight lines and label the directions as shown in the diagram on page 32.
5. Make a paper sling to hold the magnet by cutting a 1-inch × 8-inch (2.5-cm × 20-cm) strip from a second sheet of paper
6. Use the hole-punch to make a hole in each end of the paper strip.
7. Bend the strip of paper to bring the holes at each end together. Then put a 12-inch (30-cm) string through the holes, and knot the string at one end to tie the holes together.
8. Wrap a piece of paper around the magnet and secure it with tape, in order to cover up any identifying pole-markings.
9. Place the magnet in the paper sling so that the magnet hangs horizontally.
10. Hold the end of the string and hang the magnet over the paper compass taped to the table, until the magnet's ends point steadily in a north-to-south direction.
11. Use masking tape and the marking pen to label a large N and S at the ends of the magnet that are pointing north and south.

### Results

It takes about one minute for the swinging magnet to come to rest in line with the north-to-south line on the paper compass.

### Why?

A magnetic force field surrounds the earth. Any suspended magnet will align itself with this magnetic field. The north end of the hanging magnet always points to the earth's magnetic north pole, and the south end of the magnet points to the earth's magnetic south pole. Identifying the north and south pole of a magnet is called finding the polarity of the magnet.

### Let's Explore

1. Do all magnets, regardless of their shape, align with the earth's magnetic field and point in a north-to-south direction? Repeat the experiment using different-shaped magnets. Science Fair Hint: Display diagrams and photographs of hanging magnets of different shapes and sizes.
2. Does the size of the magnet affect the way it behaves? Repeat the experiment using different sizes of bar, round, and horseshoe magnets.
3. Would changing the size of the paper sling change the behavior of the magnet? Repeat the original experiment twice, first using a wider paper strip, and then using a narrower strip.

### Show Time!

1. Plastic magnetic strips found in craft stores have north and south poles on opposite sides of the strip. A 2-inch (5-cm) magnetic strip can be tested to find its polarity. Attach a piece of string to the magnetic piece, and then hang the string so that it is allowed to turn freely. Use a compass to determine the direction of the earth's magnetic north pole. Mark the north and south sides of the strip.
2. Magnetize a needle by allowing it to lie on a magnet for two minutes. Tie a thread to the center of the magnetized needle and suspend it inside a glass jar. Use a compass to determine which end of the needle points toward the north. Once you have identified the polarity of the needle, it can be used as a compass. Display the hanging compass as part of a project.

### Check It Out!

At first, the stones that attracted small pieces of iron were called Magnete stones in honor of a Greek tribe, the Magnetes. Later, the stones were called magnetite and then, when it was discovered that these suspended stones always point north, the name changed to lodestone. Write a report about the first magnets. Include the meaning of the word "lodestone," as well as information about the first crude compasses made from this north-seeking stone.